1. Field of the Invention
The present invention relates to LED traffic lights, more particularly to LED traffic light intensity controllers.
2. Background of the Invention
Traditionally, traffic lights have used light bulbs in order to produce light. A colored filter was installed in front of each bulb for giving one of the three traffic lights common colors. However, traffic lights using this technology have many drawbacks: the bulbs power consumption is high (each being between 100 W and 150 W), thus increasing the operation costs, the bulb lifetime is short and decreases with environmental conditions. For example, a light bulb's lifetime decreases with vibrations and temperature.
In recent years, LED panel arrays were proposed for replacing traditional light bulbs for traffic light applications. Recent technologies that have been developed allow the generation of all the three colors needed in such an application (red, yellow and green). An LED traffic light uses only a fraction of the electrical power a light bulb traffic light used and is thus less expensive for long term use. However, LEDs employed for making up the array have a limited lifetime and their output light intensity also decreases with time. After a period of time, the total light intensity of a color (e. g. the traffic light red color) may drop below the standard minimum intensity required in order to insure traffic safety.
LED traffic lights are also sensitive to vibrations and shocks. Therefore, current technologies using LEDs in order to replace standard traffic light bulbs are neither reliable enough nor cost-efficient for being widely implemented.